An Internet Protocol (IP) session is a session connection between a user and an IP edge device in an access network. Usually, it is necessary to perform keepalive detection for the IP session at the network side. The keepalive detection is designed to determine whether the IP session is still in the connected state, and facilitate the network side to manage the user access to the network. For example, if the IP session is still connected, the network side monitors and manages the IP session and performs charging; if the IP session is disconnected, the network side releases the resources occupied by the IP session to avoid the waste of resources.
FIG. 1 shows an IP session between the user and the network side, where “P” represents a peer of the user. In FIG. 1, n users exist at the user side; an Access Node (AN), and Edge Nodes (ENs) such as a Broadband Network Gateway (BNG) or a Broadband Remote Access Server (BRAS) exist at the network side. In FIG. 1, each user sets up an IP session with the EN through the AN. Accordingly, n users may set up n IP sessions with the EN.
In FIG. 1, when the user carries out services, the network side can provide multicast services for the user based on the multicast technology supported by the network side and the user side. In the multicast technology, if the user needs to carry out a multicast service, the user may request joining the multicast group according to the multicast group address which is notified by the network side and corresponds to the multicast service. After the network side accepts the request, the user side may obtain the network-side broadcast service information from the network side. Each multicast group may have more than one multicast group member.
Besides, in the multicast technology in the prior art, communication is performed between the user side and the network side based on the existing multicast management protocols. The existing multicast management protocols include: Internet Group Management Protocol (IGMP) applicable to IPv4, and Multicast Listener Discovery (MLD) protocol applicable to IPv6.
In the prior art, the user may carry out services based on the multicast technology. However, the keepalive detection for the IP session between the user side and the network side needs to be based on a specific IP session keepalive detection mechanism. In the existing IP session keepalive detection mechanism, the EN sends a session detection message to the corresponding user for each IP session between the user side and the network side based on the Bidirectional Forwarding Detection (BFD) protocol, for example, for the IP session between the User Equipment (UE), AN, and EN. After receiving the session detection message, the user returns a response message to the EN if the user is online.
In the prior art, few UEs at the user side support the BFD protocol. Therefore, if the user hardly supports such a protocol, the existing IP session keepalive detection mechanism can hardly monitor the IP session between the user side and the network side.
Besides, in the prior art, the IP session between the user side and the network side generally supports unicast services only, and does not support multicast services.